Personal care products require preservatives to prevent the growth of microorganisms, especially bacteria, yeast and molds. While manufacturers may take stringent precautions to prevent microbial contamination during manufacture, it is inevitable that once a product has been newly opened by a consumer, there is a significant risk of contamination and subsequent microbial growth. Such microbial growth can result in the spoilage of the consumer product, compromising its performance. It is therefore customary to add preservative agents to personal care products at the time of manufacture. Oil-in water emulsions are known to be particularly susceptible to microbial growth.
The choice of preservative agents must be carefully considered into order to balance multiple concerns. Such concerns include cost, availability, toxicity, environmental risk, irritation, compatibility with other ingredients, and robustness against microbial growth. Many common preservative compounds can be irritating at high concentrations, yet ineffective at low concentrations. Other important factors relate to the nature of the personal care product, including its manner and frequency of use, expected shelf-life, and expected duration of use. In order to optimize properties, many personal care compositions employ a mixture of preservative agents, but this requires careful optimization of the amounts of each agent. Mixed preservative systems may be difficult to formulate, but provide the added benefit that the individual ingredients may be able to inhibit microbial growth of different organisms using different mechanisms of action, thus resulting in a broader spectrum of antimicrobial activity.
Traditional preservatives used in personal care products include para-hydroxybenzoic acid derivatives (parabens), aldehydes (e.g., formaldehyde, benzaldehyde), alkyl benzoates, benzoic acid salts (e.g., sodium benzoate), formic acid salts, arylphenols ortho phenylphenol), halogenated diphenyl ethers (e.g., triclosan), quaternary ammonium compounds (e.g., cetylpyridinium chloride, benzethonium chloride, benzalkonium chloride), nitrates and nitrites, and guanidine compounds (e.g., poly(hexamethylene biguanide)).
It has become particularly commercially desirable to formulate personal care products using ingredients that minimize risks to consumer's health and environmental impact. It has been difficult to develop effective preservative systems for personal care products which use as preservatives components with low health and environmental risks.
Consequently, there is a need for new, improved preservative systems for personal care products, which are inexpensive, robust, non-irritating and compatible with personal care formulations.